Hydraulic modulator valve

Claim 1

In an hydraulic modulator of the type including a casing with a bore therein, first and second ports in said casing, a stepped spool axially and slidably engaged within said bore and forming with the circumference of the bore an annular fluid throttle passage between said ports, and spool actuating means for controlling axial displacement of the spool, the improvement wherein said stepped spool comprises a large diameter portion hermetically engaged within said bore, a small diameter portion and a medium diameter portion in sequence and both slightly lesser diameter then said bore, said throttle passage being formed by said bore and said medium and small diameter portions of said spool, wherein said spool actuating means comprises a pressure responsive means on said spool and a pressure chamber formed in the bore of said casing in open communication with said second port, resilient means for biasing said spool to its normal position such as to hold said throttle passage in the maximum length thereof, and an accumulator disposed within said pressure chamber, wherein said accumulator comprises a piston axially slidably engaged within said bore and resilient means biasing said piston toward said spool, and wherein a stopper means is provided in said pressure chamber which engages both said spool and piston when in their normal positions to limit further motion of the spool and piston toward one another.